This is a revision of application R21 DE017117-01A1 in response to the NIDCR Clinical Trial Planning Grant, PAR-06-026 (formerly PAR-03-042), with the objective of planning for a definitive phase III multi- center randomized clinical trial (RCT) to determine if fluoride varnish (FV) is effective in reducing dental caries among toddlers when it is applied to children's teeth from 3 to 36 months of age. Oral health disparity and dental caries in children, including toddlers, continue to be major public health concerns. Healthy People 2010 re-emphasized its goals to improve both oral health disparity and dental caries, particularly among young children. Fluoride varnish has been shown to be an effective preventive tool against caries in permanent teeth. Two small studies have demonstrated similar effectiveness in preschool children young as 3 years of age. However, there is no published study of FV effect in children age 6-36 months, the period when primary dentition erupts. Teeth are vulnerable to develop caries immediately after teeth eruption. Although the effectiveness of FV on primary dentition of children 3 years and younger is suggested in the literature and is supported by biological rationale, this efficacy is still uncertain. A RCT among this specific age population is needed. This proposal aims to develop the tools necessary to carry a multi-center RCT to determine if fluoride varnish is effective in reducing caries in primary dentition when applied from 6-36 months of age. Specifically, the proposal aims to: (1) develop the structure of an RCT including the Administrative Coordinating Center, Data Coordinating Center, Field Centers, Consultants, Data Safety Monitoring Board etc., and committees such as Steering, Executive, Advisory, etc.; (2) develop the process for an RCT including refinement of the hypotheses, end points, study design, protocol, procedures, and recruitment and retention strategies; (3) develop the manual of procedures (MOP) with step-by-step protocols for all study activities including the formation of committees, the recruitment, retention, and adherence methods, the conduct of forms and questionnaires, and the procedures training manual and procedures certification process. The proposed study is a two-group randomized placebo control design and will enroll between 1600 to 2000 children age 3-6 months and prior to their 6 months well-child visit. Each participating clinics will recruit between 150-200 participants. Two research networks, an HMO, and a university institution have agreed to participate in the planning grant and provide the clinic sites for the RCT. Keywords: fluoride varnish, dental caries, oral health, early prevention, multi-center, toddlers. [unreadable] [unreadable] [unreadable]